[SOLVED] Kernel Panic randomly on 2 units (rPi 1 model B)

[ghaspias]

I have also been hit by (apparently) this problem. Started with sporadic hangs or hiccups, then crashes, then kernel panics... which I had attributed to minor instability or power problems. Then I could not boot anymore. This happened about two weeks ago.
The big problem with this is that I can not access my filesystem. Usually if your linux system breaks, you can fix it manually, but how do I fix a problem if I can't even mount the affected root volume?
More troubling, is that my volume (which is an external usb drive) crashes also other systems I have attempted to use for rescue (a Fedora 22 live).
Could someone familiar with btrfs give me some hints? I am a long time linux user, but this btrfs is totally strange - it looked good, but only if it works...